I am running local rediis for my application. I am using ServiceStack.Rediis client with C#.
I am storing items as an object type T with some key.
For example
Key "1234" : {
object {
name : "abcd",
value : "1"
}
}
I am storing something like 10000 objects of same type with key. I would like to apply pagination when i retrieve these objects and only show like 20 per page.
Is this possible? If yes, what should be a good way to resolve this?
Thanks,
Vivek
Use the SCAN command with a count of 20.
Related
I'm developing a chat app. In my app there are 4 nodes called User, Recent, Message, Group. I'm using Objective-C My message object looks like,
{
"createdAt" : 1.486618017521277E9,
"groupId" : "-KcWKeXXQ9tjYsYfCknx",
"objectId" : "-KcWKftK8GiMxxAnarL5",
"senderId" : "828949592937598976",
"senderImage" : "http://hairstyleonpoint.com/wp-content/uploads/2014/10/marcello-alvarez.png",
"senderName" : "John Doee",
"status" : "Seen",
"text" : "Hi all",
"type" : "text",
"updatedAt" : 1.486622011467733E9
}
When I'm updating a User, all message's senderName should be updated accordingly. Is there are way to do this via the code or Do I need to write a rule. I'm a newbie to the firebase. Please suggest me a way to do that. If It's possible to do with the rules, Please guide me on this.
It's not possible to do this via rules, so you have to manually iterate over all your data and update the senderName.
Anyways, I think you would probably be better off with saving {senderID: $someUserID} instead - like you would do in a relational database. The userID is static, so can change the user without having to update all the instances where you use it.
I have an array of Objects that I want to store in Redis. I can break up the array part and store them as objects but I am not getting how I can get somethings like
{0} : {"foo" :"bar", "qux" : "doe"}, {1} : {"name" "Saras", "age" : 23}
and then search the db based on name and get the requested key back. I need something like this. but can't come close to getting it right.
incr id //correct
(integer) 3
get id //correct
"3"
SADD id {"name" : "Saras"} //wrong
SADD myset {"name" : "Saras"} //correct
(integer) 1
First is getting this part right.
Second is somehow getting the key from the value i.e.
if name==="Saras"
then key=1
Which I find tough. Or I can store it directly as array of objects and use a simple for loop.
for (var i = 0; i < userCache.users.length; i++) {
if (userCache.users[i].userId == userId && userCache.users[i].deviceId == deviceId) {
return i;
}
}
Kindly suggest which route is best with some implementation?
The thing I found working was storing the key as a unique identifier and stringifying the whole object while storing the data and applying JSON.parse while extracting it.
Example code:
client
.setAsync(obj.deviceId.toString(), JSON.stringify(obj))
.then((doc) => {
return client.getAsync(obj.deviceId.toString());
})
.then((doc) => {
return JSON.parse(doc);
}).catch((err) => {
return err;
});
Though stringifying and then parsing it back is a computationally heavy operation and will block the Node.js server if the size of JSON becomes large. I am probably ready to take a hit for lesser complexity because I know my JSON wouldn't be huge, but that needs to be kept in mind while going for this approach.
Redis is pretty simple key-value storage. Yes, there are other data structures like sets, but it has VERY limited query capabilities. For example, if you want to get find data by name, then you would have to to something like that:
SET Name "serialized data of object"
SET Name2 "serialized data of object2"
SET Name3 "serialized data of object3"
then:
GET Name
would return data.
Of course this means that you can't store two entries with the same names.
You can do limited text matching on keys using: http://redis.io/commands/scan
To summarize: I think you should use other tool for complex queries.
The first issue you have, SADD id {"name" : "Saras"} //wrong, is obvious since the "id" key is not of type set, it is a string type.
In redis the only access point to data is through its key.
As kiss said, perhaps you should be looking for other tools.
I want to authorize a storage with VMs. For that I need to have all the VM ID's for a storage and those I get using the following call:
https://[username]:[apikey]#api.softlayer.com/rest/v3/SoftLayer_Network_Storage_Iscsi/9653497/getAllowableVirtualGuests?objectMask=mask[id,fullyQualifiedDomainName]
This gives me all the VM ID's corresponding to 9653497 (storage/order ID). However, I need to have all those storage ID's (like 9653497) which are not assigned to any of the VM's ID. I am using below call to get all storage ID:
https://[username]:[apikey]#api.softlayer.com/rest/v3/SoftLayer_Account/getNetworkStorage?objectMask=mask[id,username,nasType,storageType, billingItem[description,location[id,longName]]]&objectFilter={"networkStorage":{"nasType":{"operation":"ISCSI"},"billingItem":{"description":{"operation":"Endurance Storage"}}}}
the data that you are using for the filter probably are wrong, try to call the get object method GET /SoftLayer_Network_Storage/9653497/getObject?objectMask=mask[nasType,billingItem[description]] and see if the values of the request are the same as of your objectFilter
The filter in your request, gets Block Storage("nasType":{"operation":"ISCSI"}), maybe you need the File Storage. We can remove it to get more "Endurance" items (Block and File).
Please try the following removing some filters:
https://[username]:[apikey]#api.softlayer.com/rest/v3/SoftLayer_Account/getNetworkStorage?objectMask=mask[id,username,nasType,storageType, billingItem[description,location[id,longName]]]&objectFilter={ "networkStorage": { "billingItem": { "description": { "operation": "Endurance Storage" } } } }
Method: GET
if we don't want to get only Endurance, we can remove that filter too.
But when trying to add some properties using objectMasks to SoftLayer_Account::getNetworkStorage like allowableVirtualGuests, that property is not present in SoftLayer_Network_Storage.
For that reason the unique way to get “getAllowableVirtualGuests” is using SoftLayer_Network_Storage::getAllowableVirtualGuests
I have something like this for every user in mongoDB:
{
"id" : 1234,
"name" : "Mr. Someone",
"userdata" : {
"living" : {
"city" : "Somecity",
"address" : "Main Street 10.",
"zip" : "1023"
},
"interest" : "Cars"
}
I'm trying to find a way to count how many subscribers live in Somecity.
My best guess was the following:
db.users.count({userdata:{living:{city:"Somecity"}}}
But the result was 0.
How can I properly count "rows" by a given value in mongoDB?
I'm using mongoDB's documentation (for example: http://docs.mongodb.org/manual/reference/sql-comparison/) but could not resolve my problem yet.
I'm using mongoDB trough shell.
I think I have found the sollution to my problem:
db.users.count({"userdata.living.city":"Somecity"})
This "dotting" method allowed me to search for only one value in the array, while the method I tried first wanted to find an exact match.
Further reading: http://docs.mongodb.org/manual/reference/operator/query/elemMatch/
Quote:
Since the $elemMatch only specifies a single condition, the $elemMatch
expression is not necessary, and instead you can use the following
query:
db.survey.find( { "results.product": "xyz" } )
Say I have a team object, that has a name property, a city property and a players property, where the players property is a an array of possibly many players. This is represented in an SQL database with a teams table and a players table, where each player has a name and a team_id.
Building a RESTful api based on this simple data-structure, I'm in doubt if there is a clear rule regarding, if the return object should/could include a list of players, when hitting /teams/:id ?
I have a view, that needs to show a team, and its players with their names, so:
1: Should /teams/:id join the two tables behind the scene and return the full team object, with a players property, that is an array of names and id's?
2: Should /teams/:id join the two tables behind the scene and return the team object, with a players property, that is an array of just id's that will then have to be queried one-by-one to /players/:id ?
3: Should two calls be made, one to /teams/:id and one to /teams/:id/players ?
4: Should a query string be used like this /teams/:id?fields=name,city,players ?
If either 2 or 3 is the way to go, how would one approach the situation, where a team could also have multiple cities, resulting in another cities table in the DB to keep it normalized? Should a new endpoint then be created at /teams/:id/cities.
When creating RESTful API's, is it the normalized datastructure in the DB that dictates the endpoints in the API?
Usually with a RESTful API, it is best that the use-cases dictate the endpoints of the API, not necessarily the data structure.
If you sometimes need just the teams, sometimes need just the players of a team, and sometimes need both together, I would have 3 distinct calls, probably something like /teams/:id, /players/:teamid and player-teams/:teamid (or something similar).
The reason you want to do it this way is because it minimizes the number of HTTP requests that need to be made for any given page. Of all of the typical performance issues, an inflated number of HTTP requests is usually one of the most common performance hits, and usually one of the easiest to avoid.
That being said, you also don't want to go so crazy that you create an over-inflated API. Think through the typical use cases and make calls for those. Don't just implement every possible combination you can think of just for the sake of it. Remember You Aren't Gonna Need It.
I'd suggest something like:
GET /teams
{
"id" : 12,
"name" : "MyTeam"
"players" :
{
"self" : "http://my.server/players?teamName=MyTeam"
},
"city" :
{
"self" : "http://my.server/cities/MyCity"
}
}
GET /cities
GET /cities/{cityId}
GET /players
GET /players/{playerId}
You can then use URIs to call out to get whatever other related resources you need. If you want the flexibility to embed values, you can use ?expand, such as:
GET /teams?expand=players
{
"id" : 12,
"name" : "MyTeam"
"players" :
{
"self" : "http://my.server/players?teamName=MyTeam",
[
{
"name" : "Mary",
"number" : "12"
},
{
"name" : "Sally",
"number" : "15"
}
]
},
"city" :
{
"self" : "http://my.server/cities/MyCity"
}
}